Pyranometers and pyrheliometers are instruments to measure hemispherical- and direct solar irradiance. This standard describes practices for evaluation of uncertainties when calibrating and when performing outdoor measurements with pyranometers and pyrheliometers. The user should realize that the measurement uncertainty as obtained during outdoor measurements is a function of: a) the instrument class, b) the calibration procedure, c) the measurement conditions and maintenance, and d) the environmental conditions. Therefore statements about the overall measurement uncertainty can only be made on an individual basis, taking all these factors into account. Instrument classification as well as calibration are described elsewhere. The specifications in the classification may serve to estimate measurement uncertainties. The classification criteria are chosen in such a way that they define maximum (worst-case) levels of uncertainty in practical field applications.
Accuracy and uncertainty specifications for radiometers are based on a wide range of approaches and data analysis techniques. This practice will provide guidelines for a applying an internationally recognized standardized approach to estimating the uncertainty in calibration of and measurements by solar pyranometers and pyrheliometers. Standardized analysis based on these recommendations will ensure the user that data collected by these radiometers can be compared based on common methods of derived uncertainty. These methods will improve the accuracy and usefulness of uncertainty estimates in a wide range of fast developing solar renewable energy applications, such as system performance and acceptance testing, resource assessment, and solar energy system design engineering.
Solar Radiometer;solar instrumentation; solar radiation
The title and scope are in draft form and are under development within this ASTM Committee.
Citing ASTM Standards
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